A control apparatus is per se known that, when the air/fuel ratio of an internal combustion engine is changed toward the rich side from the theoretical air/fuel ratio, absorbs the increase in engine torque that is caused by generation of electricity by a motor-generator (refer to Patent Document #1). This control apparatus increases the amount of fuel supplied to the internal combustion engine while taking account of the response delay in the air amount, so that the air/fuel ratio changes toward the rich side in a short time interval. Apart from the above, Patent Documents #2 and #3 in the Citation List may also be considered to have some relevance to the present invention.